Apparatus and method for measuring a three dimensional shape

ABSTRACT

Provided are an apparatus and a method for measuring a three dimensional shape with improved accuracy. The apparatus includes a stage, at least one lighting unit, a plurality of image pickup units and a control unit. The stage supports an object to be measured. The lighting unit includes a light source and a grid, and radiates grid-patterned light to the object to be measured. The image pickup units capture, in different directions, grid images reflected from the object to be measured. The control unit calculates a three dimensional shape of the object from the grid images captured by the image pickup units. The present invention has advantages in capturing grid images through a main image pickup portion and sub-image pickup portions, enabling the measurement of the three dimensional shape of the object in a rapid and accurate manner.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/463,269 filed Aug. 19, 2014, which is adivisional application of U.S. patent application Ser. No. 12/919,691,filed on Nov. 3, 2010, the disclosures of each of which are hereinincorporated by reference in their entirety. The U.S. patent applicationSer. No. 12/919,691 is a national entry of International Application No.PCT/KR2009/000904, filed on Feb. 25, 2009, which claims priority toKorean Application No. 10-2008-0017439 filed on Feb. 26, 2008, KoreanApplication No. 10-2008-0082629 filed on Aug. 23, 2008, and KoreanApplication No. 10-2009-0015691 filed on Feb. 25, 2009, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an apparatus and a method for measuringa three dimensional shape, and more particularly to an apparatus and amethod for measuring a three dimensional shape capable of increasingmeasurement precision for the three dimensional shape of a measurementtarget.

BACKGROUND ART

Generally, an apparatus for measuring a three dimensional shape is anapparatus measuring a three dimensional shape of a measurement object byradiating a grid-patterned light to the measurement object, receiving agrid image reflected from the measurement object and analyzing the gridimage.

A conventional apparatus for measuring a three dimensional shape havehad one projecting unit for radiating a grid-patterned light to ameasurement object and one imaging unit for capturing a grid imagereflected from the measurement object.

As described above, in case that a grid-patterned light is radiated atonly one side in order to measure a three dimensional shape of ameasurement object, a shadow region, at which a grid image does notarrive due to protrusion of the measurement object, is formed at theother side, thereby making it difficult to obtain a perfect threedimensional shape of the measurement object. In order to improve this,the three dimensional shape of the measurement object is measured byusing the method that a grid-patterned light is radiated again afterrotating and moving the projecting unit to the other side, but a problemof requiring relatively much measurement time occurs.

In addition, in case of capturing a grid image by using only one imagingunit, there has been a problem that a picture of a regular reflectionsurface cannot be accurately acquired due to regular reflection of themeasurement object. In order to improve this, a method, in which regularreflectivity is reduced by using a filter or a control of light amountto acquire a picture of a regular reflect surface, is sometimes used,but in this case, there occurs a problem of reduction of measurementprecision because a grid pattern of a three dimensional surface having agreat regular reflectivity appears well but a grid pattern of anperipheral area does not appear well.

DISCLOSURE OF INVENTION Technical Problem

Thus, the present invention obviates the above problems, and thus thepresent invention provides an apparatus and a method for measuring athree dimensional shape capable of enhancing productivity of measuring athree dimensional shape of a measurement object and enhancingmeasurement precision.

Technical Solution

In accordance with an aspect of the present invention, an apparatus formeasuring a three dimensional shape includes a projecting unitgenerating and radiating a grid-patterned light, an X-Y axistransferring table installed under the projecting unit to transfer aninspection object, a beam splitting unit installed between theprojecting unit and the X-Y axis transferring table to split and pass agrid image reflected from the inspection object, a plurality ofreflecting mirrors installed under the beam splitting unit and spacedapart from each other in a circumferential direction to reflect the gridimage when the grid image reflected from the inspection object isradiated, and a plurality of imaging units installed at a side of thebeam splitting unit and at sides of the plurality of reflecting mirrors,respectively, to capture the grid image passing through the beamsplitting unit and the grid image reflected from the plurality ofreflecting mirrors.

In accordance with an aspect of the present invention, a method formeasuring a three dimensional shape includes transferring an inspectionobject to a measurement location by an X-Y axis transferring table,pitch-transferring a grid element by a grid transfer instrument, afterthe inspection object is transferred to the measurement location,turning on a light source of an imaging unit to radiate a grid-patternedlight to the inspection object, after the grid element ispitch-transferred, receiving a grid image reflected from the inspectionobject via a plurality of reflecting mirrors to capture the grid imagein a plurality of imaging units, after the grid-patterned light isradiated to the inspection object, turning off the light source of theimaging unit, after the grid image is captured in the plurality ofimaging units, checking whether the grid element is pitch-transferred byN+1 times by using a control unit, after the light source of the imagingunit is turned off, turning on a first circular lamp unit or a secondcircular lamp unit and photographing the inspection object by theplurality of imaging units, after the grid element is pitch-transferredby N+1 times, checking whether measurement of the inspection object iscompleted, after the inspection object is photographed by the pluralityof imaging units, and turning on the first circular lamp unit or thesecond circular lamp unit by using the control unit and calculating athree dimensional shape of the inspection object by using an image ofthe inspection object, in which the inspection object is photographed,and the grid image captured in the plurality of imaging units, after themeasurement of the inspection object is completed.

In accordance with another aspect of the present invention, an apparatusfor measuring a three dimensional shape includes a measurement board, awork-stage, a plurality of projecting units, an imaging unit and acontrol unit. The work-stage fixes the measurement board. The pluralityof projecting units, each of which includes a light source, a gridpassing a light radiated from the light source and a projecting lenspart imaging a grid-patterned light of the grid to a measurement objectin the measurement board, radiates grid-patterned lights in differentdirections with respect to the measurement object. The imaging unitreceives a grid image reflected by the measurement object. The controlunit selectively turns on/off at least two of the plurality ofprojecting units according to a shape of the measurement object. A threedimensional shape of the measurement object is measured by using thegrid image received in the imaging unit by the at least two projectingunits that are selectively turned on.

In accordance with still another aspect of the present invention, anapparatus for measuring a three dimensional shape includes a work-stage,a plurality of projecting units, an actuator, an imaging unit and acontrol unit. The work-stage fixes a measurement board. The plurality ofprojecting units, each of which includes a light source, a grid passinga light radiated from the light source and a projecting lens partimaging a grid-patterned light of the grid to a measurement object inthe base member, is arranged in a regular polygon form so as to radiategrid-patterned lights in different directions with respect to themeasurement object, a direction in which the light radiated from thelight source advances and a normal line of the base member forming aconstant angle.

In accordance with still another aspect of the present invention, anapparatus for measuring a three dimensional shape includes a stage, atleast one lighting unit, a plurality of image pickup units, and acontrol unit. The stage supports a measurement object. The lighting unitincludes a light source and a grid and radiating a grid-patterned lightto the measurement object. The image pickup units capture a grid imagereflected from the measurement object in different directions. Thecontrol unit calculates a three dimensional shape of the measurementobject by using the grid images captured by the image pickup units. Theimage pickup units include a main image pickup portion and a pluralityof sub image pickup portions. The main image pickup portion is disposedvertical with respect to a reference surface of the stage. The sub imagepickup portions are disposed inclined with respect to the referencesurface of the stage by a constant angle, and spaced apart from eachother along a circumferential direction around the main image pickupportion. The control unit may match coordinate systems of the gridimages captured by the main image pickup portion and the sub imagepickup portions, calculate a reliability index (visibility) for each ofthe matched grid images, and apply a weight to the calculatedreliability index, to calculate the three dimensional shape of themeasurement object.

In accordance with still another aspect of the present invention, anapparatus for measuring a three dimensional shape includes a stage, atleast one lighting unit, a main image pickup portion, a sub image pickupportion, and a control unit. The stage supports a measurement object.The lighting unit radiates a grid-patterned light to the measurementobject. The main image pickup portion captures a main image out of agrid image formed by the grid-patterned light reflected from themeasurement object. The sub image pickup portion captures a sub imagethat is not incident on the main image pickup portion by regularreflection, out of the grid image formed by the grid-patterned lightreflected from the measurement object. The control unit calculates athree dimensional shape of the measurement object by using the mainimage and the sub image captured by the main image pickup portion andthe sub image pickup portion. The control unit may match coordinatesystems of the grid images captured by the main image pickup portion andthe sub image pickup portions, calculate a reliability index(visibility) for each of the matched grid images, and apply a weight tothe calculated reliability index, to calculate the three dimensionalshape of the measurement object.

In accordance with another aspect of the present invention, according toa method for measuring a three dimensional shape, firstly, a measurementobject is transferred to a measurement location by transfer of a stage.Then, a grid-patterned light is radiated to the measurement object by atleast one lighting unit. Thereafter, a grid image reflected from themeasurement object in different directions is captured by a plurality ofimage pickup units. Then, a three dimensional shape of the measurementobject is calculated by using the grid images captured by the imagepickup units. Capturing the grid image may include capturing a mainimage out of the grid image reflected from the measurement object by amain image pickup portion disposed vertical with respect to a referencesurface of the stage, and capturing a sub image that is not incident inthe main image pickup portion by regular reflection, out of the gridimage reflected from the measurement object, by a plurality of sub imagepickup portions disposed inclined with respect to the reference surfaceof the stage by a constant angle, and spaced apart from each other alonga circumferential direction around the main image pickup portion, at thesame time of capturing the main image. Calculating the three dimensionalshape of the measurement object may include matching coordinate systemsof the main image and the sub images respectively captured by the mainimage pickup portion and the sub image pickup portions, and calculatinga reliability index (visibility) for each of the matched main and subimages, and applying a weight to the calculated reliability index, tomap weight-applied data.

Advantageous Effects

According to the apparatus and the method for measuring a threedimensional shape, a three dimensional shape of a measurement object ismeasured by a plurality of projecting units or a plurality of imagingunits, thereby reducing measurement time and enhancing measurementprecision.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in con junction with the accompanyingdrawings, in which:

FIG. 1 is a structural view illustrating a structure of an apparatus formeasuring a three dimensional shape according to Embodiment 1 of thepresent invention.

FIG. 2 is a plan view illustrating a projecting unit shown in FIG. 1.

FIG. 3 is a plan view illustrating second and third light sources shownin FIG. 1.

FIG. 4 is a flow chart illustrating a method for measuring a threedimensional shape according to Embodiment 1 of the present invention.

FIG. 5 is a schematic side view illustrating an apparatus for measuringa three dimensional shape according to Embodiment 2 of the presentinvention.

FIG. 6 is a schematic plan view illustrating an exemplary embodiment ofthe apparatus for measuring a three dimensional shape shown in FIG. 5.

FIG. 7 is a schematic plan view illustrating another exemplaryembodiment of the apparatus for measuring a three dimensional shapeshown in FIG. 5.

FIGS. 8 and 9 is a plan view illustrating an operation of a liquidcrystal display panel forming a grid unit shown in FIG. 6 or FIG. 7.

FIG. 10 is a schematic plan view illustrating still another exemplaryembodiment of the apparatus for measuring a three dimensional shapeshown in FIG. 5.

FIG. 11 is a schematic plan view illustrating still another exemplaryembodiment of the apparatus for measuring a three dimensional shapeshown in FIG. 5.

FIG. 12 is a schematic view illustrating an apparatus for measuring athree dimensional shape according to Embodiment 3 of the presentinvention.

FIG. 13 is a plan view illustrating the apparatus for measuring a threedimensional shape shown in FIG. 12.

FIG. 14 is an enlarged view, in which a measurement object is enlargedso as to explain a process of measuring a three dimensional shape of ameasurement object shown in FIG. 12.

FIG. 15 is a flow chart illustrating a method for measuring a threedimensional shape according to Embodiment 3 of the present invention.

MODE FOR THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the annexed drawings.

Embodiment 1

FIG. 1 is a structural view illustrating a structure of an apparatus formeasuring a three dimensional shape according to Embodiment 1 of thepresent invention. FIG. 2 is a plan view illustrating a projecting unitshown in FIG. 1. FIG. 3 is a plan view illustrating second and thirdlight sources shown in FIG. 1. A first circular lamp unit 60 or a secondcircular lamp unit 70 shown in FIG. 1 is respectively shown in a sidecross-sectional status. A first circular lamp unit 60 or a secondcircular lamp unit 70 in FIG. 2 is respectively shown in a plancross-sectional status.

As shown in FIGS. 1 to 3, an apparatus for measuring a three dimensionalshape according to the present embodiment includes a projecting unit 10,an X-Y axis transferring table 20, a beam splitting unit 30, a pluralityof reflecting mirrors 40 and a plurality of imaging units 50, and eachelement is described as follows.

The projecting unit 10 generates and radiates a grid-patterned light,and the X-Y axis transferring table 20 is installed under the projectingunit 10 to transfer an inspection object P. The beam splitting unit 30is installed between the projecting unit 10 and the X-Y axistransferring table 20 to split and pass a grid image reflected from theinspection object P. The plurality of reflecting mirrors 40 is installedunder the beam splitting unit 30 and spaced apart from each other in acircumferential direction to reflect the grid image when the grid imagereflected from the inspection object P is radiated. The plurality ofimaging units 50 is installed at a side of the beam splitting unit 30and at sides of the plurality of reflecting mirrors 40, respectively, tocapture the grid image passing through the beam splitting unit 30 andthe grid image reflected from the plurality of reflecting mirrors 40.

The detail structure of the projecting unit 10, the X-Y axistransferring table 20, the beam splitting unit 30, the plurality ofreflecting mirrors 40 and the plurality of imaging units 50 forming theapparatus for measuring a three dimensional shape according to thepresent embodiment is described as follows.

The projecting unit 10 includes a light source 11, a grid element 12, agrid transfer instrument 13, a projecting lens 14 and a projecting lensfilter 15.

The light source 11 of the projecting unit 10 generates and radiates alight. The grid element 12 is installed under the light source 11 andconverts the light radiated from the light source 11 into agrid-patterned light and radiates the grid-patterned light. Aninclination angle g of the grid element 12 that converts the light intothe grid-patterned light is 45 degrees with respect to Y-axis directionof an X-Y plane, as shown in FIG. 2. The grid transfer instrument 13employs a PZT (piezoelectric), which is installed at the grid element 12to transfer the grid element 12, and the projecting lens 14 is installedunder the grid element 12 to project the grid-patterned light. Theprojecting lens filter 15 is installed under the projecting lens 14 tofilter and radiate the grid-patterned light radiated via the projectinglens 14.

X-Y axis transferring table 20 includes a motor 21 to move the X-Y axistransferring table 20 in an X-axis direction and a motor 22 to move theX-Y axis transferring table 20 in a Y-axis direction, and align theinspection object P or transfer the inspection object P to a measurementlocation.

The beam splitting unit 30 employs a beam splitter to radiate a gridimage generated by the projecting unit 10 or an image formed by thelight that is generated from the first circular lamp unit 60 or thesecond circular lamp unit 70 and radiated to and reflected from theinspection object P, to one imaging unit 50 of the plurality of imagingunits 50, which is installed at a side of the beam splitting unit 30.

The plurality of reflecting mirrors 40 is installed inclined withrespect to an X-axis direction to radiate the grid image reflected fromthe inspection object P to the remaining plurality of imaging units 50except the imaging unit 50 installed corresponding to the beam splittingunit 30, and spaced apart from each other in a circumferentialdirection. In other words, the plurality of reflecting mirrors 40 isinstalled apart from each other by a regular interval along a circleshown in a dotted line in FIG. 3.

The plurality of imaging units 50 simultaneously captures the grid imagereflected from the reflecting mirror 40, and each of the imaging units50 includes a camera filter 51, an imaging lens 52 and a camera 53. Thecamera filter 51 filters and radiates the grid image reflected from thereflecting mirror 40. The camera filter 51 filtering the grid imageemploys one of a frequency filter, a color filter and a light intensitycontrol filter. The imaging lens 52 is installed at a side of the camerafilter 51 to image the grid image filtered by the camera filter, and thegrid image that is imaged and radiated by the imaging lens 52 iscaptured by the camera 53. The camera 53 is installed at a side of theimaging lens 52 to capture the grid image radiated from the imaging lens52.

The apparatus for measuring a three dimensional shape having the abovestructure according to the present embodiment further includes a firstcircular lamp unit 60 and a second circular lamp unit 70 to capture atwo-dimensional image for extracting a specific shape of the inspectionobject P, i.e., a light image, and a control unit 80 is further providedto control the above elements.

The first circular lamp unit 60 and the second circular lamp unit 70further provided to the apparatus for measuring a three dimensionalshape are described as follows.

The first circular lamp unit 60 is installed under the beam splittingunit 30 to generate and radiate a light to the inspection object P sothat a light image is reflected from the inspection object P. The secondcircular lamp unit 70 is installed under the plurality of reflectingmirrors 40 to generate and radiate a light to the inspection object P sothat a light image is reflected from the inspection object P. The firstcircular lamp unit 60 and the second circular lamp unit 70 radiating thelight to the inspection object P respectively includes circular ringmembers 61 and 71 and a plurality of light generating elements 62 and72.

The circular ring members 61 and 71 have throughholes 61 a and 71 a topass the grid-patterned light or the grid image. The throughhole 71 a ofthe second circular lamp unit 70 has a diameter greater than thethroughhole 61 a of the first circular lamp unit 60 so that the lightradiated from the first circular lamp unit 60 is radiated to theinspection object P or the grid image reflected from the inspectionobject P is radiated to the plurality of reflecting mirrors 40. Theplurality of light generating elements 62 and 72 is installed under thecircular ring members 61 and 71 to radiate a light.

After the light is generated from the first circular lamp unit 60 or thesecond circular lamp unit 70 and radiated to the inspection object P,the light image reflected from the inspection object P is radiated tothe beam splitting unit 30 and the plurality of reflecting mirrors 40.The light image radiated to the beam splitting unit 30 and the pluralityof reflecting mirrors 40 is captured by the plurality of imaging units50, respectively.

The grid image or the light image captured by the plurality of imagingunits 50 is received in the control unit 80. After receiving the gridimage or the light image, the control unit 80 calculates the threedimensional shape of the inspection object P by using the grid image orthe light image. The control unit 80 calculating the three dimensionalshape of the inspection object P generally controls the apparatus formeasuring a three dimensional shape according to the present embodiment,such as the projecting unit 10, the X-Y axis transferring table 20, theplurality of imaging units 50, the first circular lamp unit 60, thesecond circular lamp unit 70, etc.

A method for measuring a three dimensional shape using the apparatus formeasuring a three dimensional shape having the above structure accordingto the present embodiment is described as follows with reference toFIGS. 1 and 4 attached herewith.

As shown in FIGS. 1 and 4, in a method for measuring a three dimensionalshape according to the present embodiment, firstly, the inspectionobject P is transferred to a measurement location by the X-Y axistransferring table 20 in step S10. After the inspection object P istransferred to the measurement location, the grid element 12 ispitch-transferred by the grid transfer instrument 13 in step S20. Afterthe grid element 12 is pitch-transferred, the light source 11 of theprojecting unit 10 is turned on to radiate the grid-patterned light tothe inspection object P in step S30.

After the grid-patterned light is radiated onto the inspection object P,a grid image reflected from the inspection object P is received via theplurality of reflecting mirrors 40 to capture the grid image in theplurality of imaging units 50 in step S40. When capturing the gridimage, the plurality of imaging units 50 simultaneously captures thegrid image. After the grid image is captured by the plurality of imagingunits 50, the light source 11 of the imaging unit 50 is turned off instep S50.

After the light source 11 of the imaging unit 50 is turned off, thecontrol unit 80 checks whether the grid element 12 is pitch-transferredby N+1 times in step S60. Step S60, in which it is checked whether thegrid element 12, is pitch-transferred by N+1 times or not, returns stepS20, in which grid element 12 is pitch-transferred, when the gridelement 12 is not pitch-transferred by N+1 times. In other words, incase that the three dimensional shape of the inspection object P iscalculated by using 4-bucket algorithm, the grid element 12 is 4 timestransferred by a pitch interval thereof.

When the grid element 12 is pitch-transferred by N+1 times, the firstcircular lamp unit 60 or the second circular lamp unit 70 is turned on,and then the inspection object P is photographed by the plurality ofimaging units 50 in step S70. In other words, two dimensional image ofthe inspection object P, i.e., a light image is captured.

A method of capturing the light image is described in detail as follows.Firstly, when the grid element 12 is pitch-transferred by N+1 times, thefirst circular lamp unit 60 is turned on in step S71. After the firstcircular lamp unit 60 is turned on, the inspection object P isphotographed by the plurality of imaging units 50 in step S72. After theinspection object P is photographed by the plurality of imaging units50, the first circular lamp unit 60 is turned off in step S73. After thefirst circular lamp unit 60 is turned off, the second circular lamp unit70 is turned on in step S74. After the second circular lamp unit 70 isturned on, the inspection object P is photographed by the plurality ofimaging units 50 in step S75. After the inspection object P isphotographed by the plurality of imaging units 50, the second circularlamp unit 70 is turned off in step S76. As described above, the lightimage is captured by the plurality of imaging units 50 according to thelight generated from the first circular lamp unit 60 or the secondcircular lamp unit 70, and thus specific things of the inspection objectP in various directions may be more rapidly photographed.

After the light image is captured and the inspection object P isphotographed by the plurality of imaging units 50, it is checked whethermeasurement of the inspection object P is completed or not in step S80.Step S80, in which it is checked whether the measurement of theinspection object P is completed or not, returns step of transferringthe inspection object P to the measurement location, when themeasurement of the inspection object P is not completed. On thecontrary, when the measurement of the inspection object P is completed,the control unit 80 turns on the first circular lamp unit 60 or thesecond circular lamp unit 70, and then calculates the three dimensionalshape of the inspection object P by using the measured image of theinspection object P and the grid image measured by the plurality ofimaging units 50 in step S90.

As described above, the inspection object is simultaneously photographedby using the plurality of imaging units to calculate the threedimensional shape of the inspection object, thereby reducing measuringtime of the three dimensional shape of the inspection object.

Embodiment 2

FIG. 5 is a schematic side view illustrating an apparatus for measuringa three dimensional shape according to Embodiment 2 of the presentinvention.

Referring to FIG. 5, an apparatus for measuring a three dimensionalshape 100 according to the present embodiment includes a work-stage 130,a plurality of projecting units 110, an imaging unit 150 and a controlunit 140.

The work-stage 130 fixes a measurement board 120. The measurement board120 includes a measurement object A.

The work-stage 130 transfers and fixes the measurement board 120 in anx-axis direction or a y-axis direction. After the measurement board 120is transferred and fixed by control of the control unit 140, a firstassistant light source 160 and a second assistant light source 170radiate lights to the measurement object A, and an entire measurementarea of the measurement board 120 is set by using an identification markindicated at the measurement board 120.

The plurality of projecting units 110 is disposed to radiate lights at aconstant angle with respect to a normal line of the measurement board120. In addition, the plurality of projecting units 110 is arrangedsymmetrical to the normal line.

The plurality of projecting units 110 radiates a grid-patterned lighttoward the measurement object A. To this end, each of the plurality ofprojecting units 110 includes a light source 111, a grid unit 112passing the light radiated from the light source 111 and a projectinglens part 113 imaging the grid-patterned light of the grid unit 112 onthe measurement object A.

The light passing through the grid unit 112 forms the grid-patternedlight. To this end, the grid unit 112 includes a blocking portion (notshown) and a passing portion (not shown). The blocking portion blocksthe light radiated from the light source 111, and the passing portionpasses the light. The grid unit 112 may be formed in a various form. Thegrid unit 112 will be described later.

The projecting lens part 113 may be formed, for example, by combinationof a plurality of lenses, and focuses the grid-patterned light formed bypassing through the grid unit 112 to image the grid-patterned light onthe measurement object A disposed over the measurement board 120.

The imaging unit 150 receives a grid image reflected by the measurementobject A. The imaging unit 150 includes, for example, a camera 151 and areceiving lens part 152. The grid image reflected by the measurementobject A is captured by the camera 151 via the receiving lens part 152.

The control unit 140 may include an operation control unit 141 and ashape detecting section 142. The control unit 140 controls thework-stage 130, the projecting unit 110 and the imaging unit 150, andthe shape detecting section 142 grasps the shape of the measurementobject A located at the measurement board 120. In addition, in case thatthere exists data information capable of knowing the shape of themeasurement object A of the measurement board 120 in advance, the datainformation may be used without grasping the shape of the measurementobject A.

The control unit 140 may select and turn on even numbered projectingunits 110, and the turned on even numbered projecting units 110 may besymmetrical with respect to the measurement object. When capturing thegrid image at only one side, since an area, in which the grid image isnot radiated at the other side of the measurement object A, is formeddue to the measurement object A having a protruded three dimensionalshape, an accurate three dimensional shape is not measured. Thus, thethree dimensional shape may be more accurately measured by measuring theshape at the opposite side again.

For example, the control unit 140, in case that the measurement object Agrasped by the shape detecting section 142 has a quadrangular shape, twoprojecting units 110 may be turned on, and in case that the measurementobject A grasped by the shape detecting section 142 has an ellipticshape, more than or equal to 50% of the plurality of projecting units110 may be turned on.

According to the apparatus for measuring a three dimensional shape 100of the present embodiment, the plurality of projecting units 110 isdisposed at locations symmetrical to each other, and thus time requiredfor measurement may be reduced to increase inspection efficiency incomparison with a conventional apparatus for measuring a threedimensional shape, in which a projecting unit is moved and captures agrid image at an opposite side.

FIG. 6 is a schematic plan view illustrating an exemplary embodiment ofthe apparatus for measuring a three dimensional shape shown in FIG. 5.FIG. 7 is a schematic plan view illustrating another exemplaryembodiment of the apparatus for measuring a three dimensional shapeshown in FIG. 5.

Referring FIGS. 5, 6 and 7, the projecting units 110 are arranged in anequilateral polygon form. For example, the projecting units 110 may bearranged in a square form (FIG. 2), a regular hexagon (FIG. 3), etc.

In the present embodiment, the grid unit 112 shown in FIG. 5 may employa liquid crystal display panel 112 a. In case that the grid-patternedlight is formed by using the liquid crystal display panel 112 a, agraphic card (not shown) controlling a grid picture of the liquidcrystal display panel 112 a and a power supply part (not shown)providing the liquid crystal display panel 112 a with a power source maybe further provided. In case of using the liquid crystal display panel,an actuator for transferring a grid may not be necessary in comparisonwith using a real grid.

FIGS. 8 and 9 is a plan view illustrating an operation of a liquidcrystal display panel forming a grid unit shown in FIG. 6 or FIG. 7.

Referring to FIG. 8, a blocking portion 401 and a passing portion 402are displayed on the liquid crystal display panel 102. The blockingportion 401 blocks a light, and the passing portion 402 passes a light,thereby projecting the grid-patterned light to the measurement object A.

In order to precisely measure a three dimensional shape, thegrid-patterned light is transferred by a value that is obtained byequally dividing a pitch P by n and projected to the measurement objectA (In FIG. 9, for example, the blocking portion 401 and the passingportion 402 are transferred by 4-bucket, i.e., by a value equallydivided as ¼ of the pitch P).

Accordingly, an actuator for transferring a grid may not be provided inthe projecting unit.

FIG. 10 is a schematic plan view illustrating still another exemplaryembodiment of the apparatus for measuring a three dimensional shapeshown in FIG. 5. FIG. 11 is a schematic plan view illustrating stillanother exemplary embodiment of the apparatus for measuring a threedimensional shape shown in FIG. 5. The apparatus for measuring a threedimensional shape shown in FIGS. 10 and 11 is substantially the same asthe apparatus for measuring a three dimensional shape shown in FIGS. 6and 7 except that the grid unit formed at the projecting unit employs agrid 112 b instead of the liquid crystal display panel 112 a, andfurther includes an actuator 601 for operating the grid 112 b. Thus, thesame reference numerals are indicated to the same or similar elements,and any further description will be omitted.

Referring to FIGS. 10 and 11, an apparatus for measuring a threedimensional shape according to an exemplary embodiment of the presentinvention employs a grid 112 b, which is different from the apparatusfor measuring a three dimensional shape having the grid unit 112 usingthe liquid crystal display panel 112 a in FIG. 6 or 7. The grid 112 bmay be formed, for example, by printing a grid pattern on a glass plateto form a blocking portion and a passing portion. Two grids may beformed together on the glass plate and used in adjacent projectingunits.

As described above, in case of employing the grid 112 b, an actuator 601is formed to finely transfer the grid 112 b.

The apparatus for measuring a three dimensional shape according to thepresent embodiment includes a plurality of projecting units arranged atvertices of an equilateral polygon, and the grids 112 b formed at twoadjacent projecting units is transferred by one actuator 601. Theactuator 601 may employ a PZT.

When adjacent projecting units of the plurality of projecting units aresequentially operated, operation directions of the actuator 601 maypreferably be opposite. More particularly, after a grid 112 b {circlearound (1)} is moved in an arrow a direction and the grid-patternedlights are projected to the measurement object A, a grid 112 b {circlearound (2)} of adjacent projecting unit is moved in an arrow b directionand the grid-patterned lights are projected.

More particularly, the grid-patterned light is radiated to themeasurement object A via the grid 112 b {circle around (1)}, and theimaging unit receives the grid image reflected by the measurement objectby selected times (for example, four times). Then, the grid-patternedlight is radiated to the measurement object A via the grid 112 b {circlearound (2)}, the imaging unit receives the grid image reflected by themeasurement object by selected times (for example, four times).Likewise, a grid {circle around (3)} and a grid {circle around (4)} areperformed the same. The control unit calculates an accurate threedimensional shape of the measurement object, in which a shadow region(an area at which the grid-patterned light at a side of the measurementobject does not arrive when the grid-patterned light is projected at anopposite side of the measurement object, because the measurement objecthas a three dimensional shape) is compensated by using the received 16grid images in total. For example, shadow regions {circle around (1)}and {circle around (3)} are compensated by using values of grid image{circle around (1)} and {circle around (3)}, and values of shadowregions {circle around (2)} and {circle around (4)} are compensated byusing values of grid images {circle around (2)} and {circle around (4)}.The values of shadow regions are replaced by values corresponding toopposite areas to be compensated.

The actuator 601 employed in the apparatus for measuring a threedimensional shape according to the present embodiment simultaneouslyoperates the grids 112 b formed at the two adjacent projecting units.Thus, the number of the actuators 601 may be reduced to a half of thenumber of the projecting units.

Also, since a transfer direction of the actuator 601 contrarily operatesdirection of the grid 112 b when the adjacent projecting units aresequentially operated, time required for operation may be reduced.

Embodiment 3

FIG. 12 is a schematic view illustrating an apparatus for measuring athree dimensional shape according to Embodiment 3 of the presentinvention. FIG. 13 is a plan view illustrating the apparatus formeasuring a three dimensional shape shown in FIG. 12.

Referring to FIGS. 12 and 13, an apparatus for measuring a threedimensional shape 300 according to the present embodiment includes astage 320 supporting a measurement object 310, at least one lightingunit 330, a plurality of image pickup units 340 and a control unit 350.

The stage 320 supports the measurement object 310, and moves in anx-axis and a y-axis according to control of the control unit 350 totransfer the measurement object 310 to a measurement location.

The lighting unit 330 radiates a grid-patterned light 410 to themeasurement object 310 fixed to the stage 320. The lighting unit 330 isdisposed inclined with respect to a reference surface of the stage 320by a constant angle. The apparatus for measuring a three dimensionalshape 300 may include a plurality of lighting units 330 to increasemeasurement precision. For example, the apparatus for measuring a threedimensional shape 300 may include four lighting units 330 as shown inFIG. 13. The lighting units 330 are spaced apart from each other along acircumferential direction around the main image pickup portion that isdisposed perpendicular to the reference surface of the stage 320.Especially, the lighting units 330 may be disposed symmetrical withrespect to the normal line of the reference surface of the stage 320.Thus, the plurality of lighting units 330 radiates the grid-patternedlight 410 in different directions with respect to the measurement object310 at a constant time interval. The apparatus for measuring a threedimensional shape 300 may have the various numbers of lighting units330, such as 2, 3, 6, etc.

Each lighting unit 330 includes a light source 332 and a grid 334. Inaddition, each lighting unit 330 may further include a grid transferinstrument 336 and a projecting lens part 338.

The light source 332 radiates a light toward the measurement object 310.The grid 334 converts the light radiated from the light source 332 intothe grid-patterned light 410 according to grid pattern. The grid 334 istransferred by a grid transfer instrument 336 such as a piezoelectricactuator (PZT), etc. by 2π/n per one time and n times so as to generatethe phase-transited grid-patterned light 410. The ‘n’ is a naturalnumber greater than or equal to 2. The projecting lens part 338 projectsthe grid-patterned light 410 generated by the grid 334 to themeasurement object 310. The projecting lens part 338 may be formed, forexample, by combination of a plurality of lenses, and focuses thegrid-patterned light 410 formed via the grid 334 to project thegrid-patterned light 410 to measurement object 310. Thus, each lightingunit 330 transfers the grid 334 by n times, and the grid-patterned light410 is radiated to the measurement object 310 at each transfer.

The apparatus for measuring a three dimensional shape 300 according tothe present embodiment includes a plurality of image pickup units 340 tocapture the grid image 420 formed by the grid-patterned light 410, whichis radiated from the lighting unit 330, reflected from the measurementobject 310 in different directions.

Particularly, the apparatus for measuring a three dimensional shape 300includes a main image pickup portion 340 a disposed over the stage 320and vertical with respect to the reference surface of the stage 320, anda plurality of sub image pickup portions 340 b disposed inclined withrespect to the reference surface of the stage 320 by a constant angle.For example, the apparatus for measuring a three dimensional shape 300may include four sub image pickup portions 340 b as shown in FIG. 13.The sub image pickup portions 340 b are spaced apart from each otheralong a circumferential direction around the main image pickup portion340 a. Especially, the sub image pickup portions 340 b may be disposedsymmetrical with respect to the normal line of the reference surface ofthe stage 320. Thus, the main image pickup portion 340 a and the subimage pickup portions 340 b simultaneously capture the grid image 420reflected from the measurement object 310 in different directionsaccording to operation of each lighting unit 330. The apparatus formeasuring a three dimensional shape 300 may include the various numbersof sub image pickup portions 340 b such as 2, 3, 6, etc.

Each of the main image pickup portion 340 a and the sub image pickupportions 340 b may include a camera 342 and an imaging lens part 344 forcapturing the grid image 420. The camera 342 may employ a CCD camera ora CMOS camera. Thus, the grid image 420 reflected from the measurementobject 310 is imaged by the imaging lens part 344 and captured by thecamera 342.

The lighting units 330 and the sub image pickup portions 340 b may be onthe same concentric circle around the main image pickup portion 340 a.Alternatively, the lighting units 330 may be on a concentric circledifferent from the sub image pickup portions 340 b. In addition, thelighting units 330 may be installed at a height different from or at thesame height as the sub image pickup portions 340 b. Each of the lightingunits 330 may be disposed between the sub image pickup portions 340 b.Alternatively, when the lighting units 330 is installed at a heightdifferent from the sub image pickup portions 340 b, the lighting units330 may be installed at the same location as the sub image pickupportions 340 b.

The control unit 350 generally controls operations of the elementsincluded in the apparatus for measuring a three dimensional shape 300.The control unit 350 controls transfer of the stage 320 to locate themeasurement object 310 to the measurement location. The control unit 350sequentially operates the plurality of lighting units 330. The controlunit 350 transfers the grid 334 of each lighting unit 330 by n times,and controls the lighting unit 330 to radiate the grid-patterned light410 to the measurement object 310 at each transfer. The control unit 350controls the plurality of image pickup units 340 to simultaneouslycapture the grid image 420 reflected from the measurement object 310.

The control unit 350 calculates the three dimensional shape of themeasurement object 310 by using the grid images 420 captured by the mainimage pickup portion 340 a and the sub image pickup portions 340 b. Forexample, the control unit 350 matches coordinate systems of the gridimages 420 captured by the main image pickup portion 340 a and the subimage pickup portions 340 b. In addition, the control unit 350calculates a reliability index (visibility) for each grid image 420 byusing n values measured using an n-bucket algorithm in each of the mainimage pickup portion 340 a and the sub image pickup portions 340 b, frommathematical equations 1 and 2 as follows, and applies a weight to thecalculated 5 reliability indices, to map weight-applied data andcalculate final measurement value.

$\begin{matrix}{I_{o} = \frac{I_{1} + I_{2} + I_{3} + I_{4}}{4}} & {{Mathematical}\mspace{14mu}{Equation}\mspace{14mu} 1} \\{V = \frac{\sqrt{\left( {I_{4} - I_{2}} \right)^{2} + \left( {I_{1} - I_{3}} \right)^{2}}}{2I_{0}}} & {{Mathematical}\mspace{14mu}{Equation}\mspace{14mu} 2}\end{matrix}$

In mathematical equations 1 and 2, I₁, I₂, I₃, and I₄ indicateintensities of the grid images measured by 4 times through a 4-bucketalgorithm in each image pickup unit, for one point, and V indicates areliability index of the grid image measured in each image pickup unit,which is calculated by using them.

The control unit 350 may calculate the three dimensional shape of themeasurement object 310 by using only grid images 420 measured in themain image pickup portion 340 a and one or two sub image pickup portions340 b adjacent to lighting unit 330 under operation.

FIG. 14 is an enlarged view, in which a measurement object is enlargedso as to explain a process of measuring a three dimensional shape of ameasurement object shown in FIG. 12.

Referring to FIGS. 12 and 14, the measurement object 310 may include acircuit board 312 and an electronic element 316 on the circuit board312, which are coupled by a solder 314.

The grid-patterned light 410 is radiated from the lighting unit 330, andreflected from the measurement object 310 to generate the grid image420. Since the solder 314 connecting the electronic element 316 to thecircuit board 312 has a characteristic of a mirror surface, a regularreflection occurs at the solder 314. Thus, the grid image 420 reflectedfrom a part area out of an area of the solder 314 is upwardly reflectedand enters the main image pickup portion 340 a, but the grid image 420reflected from a remaining part area is reflected to be inclined by apredetermined angle and does not enter the main image pickup portion 340a. Instead, the grid image 420 reflected from the measurement object 310to be inclined by the predetermined angle is captured by the sub imagepickup portion 340 b. In other words, a main image that is upwardlyreflected, out of the grid image 420 by the grid-patterned light 410reflected from the measurement object 310, is captured by the main imagepickup portion 340 a, and a sub image that is regularly reflected to beinclined by the predetermined angle and does not enter the main imagepickup portion 340 a, out of the grid image 420 by the grid-patternedlight 410 reflected from the measurement object 310, is captured by theat least one sub image pickup portion 340 b. Thus, the main imagecaptured by the main image pickup portion 340 a and the sub imagecaptured by the sub image pickup portion 340 b are properly combined toprecisely measure the total three dimensional shape of the measurementobject 310 including the area of the solder 314.

FIG. 15 is a flow chart illustrating a method for measuring a threedimensional shape according to Embodiment 3 of the present invention.

Referring to FIGS. 12 and 15, in order to measure the three dimensionalshape of the measurement object 310, the control unit 350 transfers thestage 320 to transfer the measurement object 310 to the measurementlocation in step S100.

After the measurement object 310 is located to the measurement location,the grid-patterned light 410 is radiated to the measurement object 310by the at least one lighting unit 330 in step S200. For example, theplurality of lighting units 330 inclined by a constant angle withrespect to the reference surface of the stage 320 and spaced apart fromeach other along a circumferential direction around the main imagepickup portion 340 a is sequentially operated to sequentially radiatethe grid-patterned light 410. Each lighting unit 330 radiates thegrid-patterned light 410 to the measurement object 310 at each transferwhile transferring the grid 334 by n times.

After the grid-patterned light 410 is radiated to the measurement object310, the grid image 420 reflected from the measurement object 310 iscaptured in different directions by the plurality of image pickup units340 in step S300. Particularly, the main image that is toward an upperdirection out of the grid image 420 reflected from the measurementobject 310 is captured by the main image pickup portion 340 a disposedperpendicular to the reference surface of the stage 320. At the sametime, the sub image that is regularly reflected from the measurementobject 310 to be inclined by the predetermined angle and does not enterthe main image pickup portion 340 a, out of the grid image 420 reflectedfrom the measurement object 310 is captured by sub image pickup portions340 b disposed inclined with respect to the reference surface of thestage 320 by a constant angle, and spaced apart from each other along acircumferential direction around the main image pickup portion 340 a.

Thereafter, the control unit 350 matches coordinate systems of the mainimage and the sub images captured by the main image pickup portion 340 aand the sub image pickup portions 340 b in step S400. In other words,since there occurs a path difference when the grid image 420 reflectedfrom the measurement object 310 arrives at the main image pickup portion340 a and the sub image pickup portions 340 b, the path differenceincurs difference between the grid images 420 captured by the main imagepickup portion 340 a and the sub image pickup portions 340 b. Thus, thedifference between grid images 420 due to the path difference iscompensated to make coordinate systems of the main image and the subimages coincident with each other.

Then, the control unit 350 maps the main image and the sub images basedon the reliability index (visibility) of each of the main image and thesub images that are matched, to calculate the three dimensional shape ofthe measurement object 310 in step S500. For example, the control unit350 calculates the reliability index (visibility) of each of the mainimage and the sub images by using the above mathematical equations 1 and2, and applies a weight to the calculated 5 reliability indices, tocalculate the three dimensional shape of the measurement area of themeasurement object 310 by using the weight-applied data. For example,reliability of the final measurement value may be enhanced by applyingan image over a specific value among the calculated 5 reliabilityindices to a great weight, and applying an image below a specific valueamong the calculated 5 reliability indices to a low weight or to beexcluded.

As described above, a process of capturing the grid image 420 by themain image pickup portion 340 a and the sub image pickup portions 340 bis repetitively performed whenever the lighting unit 330 radiates thegrid-patterned light 410, and the control unit 350 finally measures thethree dimensional shape of the measurement object 310 by using theimages obtained from the repetitive capture.

As described above, together with the main image pickup portion 340 afor capturing the main image out of the grid image 420 reflected fromthe measurement object 310, the sub image pickup portions 340 b areadditionally installed for capturing the sub image that is regularlyreflected from the measurement object 310 and is not captured by themain image pickup portion 340 a, to more precisely measure the threedimensional shape of the measurement object 310.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

An apparatus and a method for measuring a three dimensional shape of thepresent invention may be applied to a field of measuring a threedimensional shape of a measurement object such as a printed circuitboard, a solder, etc.

The invention claimed is:
 1. An apparatus for measuring a three dimensional shape, comprising: a transferring table on which an inspection object is to be placed; a projecting unit configured to radiate a first light in a grid pattern to the inspection object, an intensity of the first light in the grid pattern being uniform along a direction of the grid pattern; a plurality of imaging units configured to capture grid images generated from the first light reflected off of the inspection object, the plurality of imaging units being arranged in a plurality of different directions to capture the grid images including different sides of the inspection object; and a control unit configured to operate the plurality of imaging units such that the plurality of imaging units capture the grid images simultaneously and to calculate the three dimensional shape of the inspection object based on the grid images captured by the plurality of imaging units; wherein each of the plurality of imaging units is arranged to be oblique to the direction of the grid pattern on a plane of the transferring table in a plan view of the transferring table.
 2. The apparatus of claim 1, further comprising: at least one lamp unit installed above the transferring table and radiating a second light to the inspection object, wherein the plurality of imaging units are further configured to capture light images generated from the second light reflected off the inspection object, and wherein the control unit is further configured to calculate the three dimensional shape of the inspection object based on the grid images and the light images.
 3. The apparatus of claim 2, further comprising: An additional imaging unit capturing a light image generated from the second light reflected off of the inspection object, Wherein the control unit is further configured to calculate the three dimensional shape of the inspection object based on the grid images, the light images captured by the plurality of imaging units, and the light image captured by the additional imaging unit.
 4. The apparatus of claim 3, wherein the light image are two dimensional image of the inspection object.
 5. The apparatus of claim 3, further comprising: a beam splitting unit installed between the projecting unit and the transferring table to pass the first light in the grid pattern and receive and pass the light image for the additional imaging unit reflected from the inspection object.
 6. The apparatus of claim 1, wherein the number of the plurality of the imaging units is four, and wherein the two imaging units in each of two pairs of the imaging units are arranged oppositely with the inspection object at a center of the two imaging units.
 7. The apparatus of claim 1, wherein the plurality of imaging units are arranged to be on a same concentric circle with the inspection object at a center of the plurality of imaging units.
 8. The apparatus of claim 1, wherein the control unit is further configured to match coordinate system of the grid images to calculate the three dimensional shape of the inspection object.
 9. The apparatus of claim 1, wherein the control unit is further configure to: calculate a reliability index of each of the grid images, apply a weight to the reliability index, and calculate the three dimensional shape of the inspection object based on the weight-applied reliability index.
 10. The apparatus of claim 1, wherein the first light in the grid pattern is oblique with respect to the Y-axis direction of an X-Y plane of the transferring table.
 11. The apparatus of claim 1, wherein the inspection object has a quadrangular shape, and wherein the grid pattern on the inspection object is oblique to edges of the inspection object. 